Method Of Manufacturing A Filter Element

ABSTRACT

The invention relates to a method of manufacturing a filter element for use in connection with e.g. gas turbines and comprising a hollow outer insert in which a hollow inner insert is arranged centrally relative to the outer insert, said inserts comprising end edges to which a top flange is secured at one end, said inserts being stiffened by a net ( 6 ), said net ( 6 ) being made by applying a liquid mass ( 5 ) to the outer and/or inner side of the filter element (I) by means of one or more nozzles ( 4, 6 ), said nozzles ( 4,7 ) being movable relative to the filter element ( 1 ), one or more nozzles ( 4, 7 ) being stationary in the longitudinal direction of the filter element ( 1 ) during the application of moulding mass ( 5 ) in one or more rings ( 8 ), while the filter element ( 1 ) rotates a number of rotations about its longitudinal axis, on which one or more nozzles ( 4, 7 ) oscillate with an oscillation greater than or equal to the distance between two rings ( 8 ) and smaller than or equal to the length of the filter element ( 1 ) for the application of connecting lines ( 9 ) between the rings ( 8 ). The invention also relates to a filter element ( 1 ) manufactured by the method, wherein the stiffening ( 6 ) of the filter element ( 1 ) is formed by a solidified moulding mass ( 5 ), and the filter element ( 1 ) is made of combustible materials.

THE PRIOR ART

The present invention relates to a method of manufacturing a filterelement for use in connection with e.g. gas turbines and comprising ahollow outer insert in which a hollow inner insert is arranged centrallyrelative to the outer insert, said inserts comprising end edges to whicha top flange is secured, said inserts being stiffened by a net.

The invention also relates to a filter element manufactured by themethod.

DK Patent 174840 discloses a filter element in which all the componentsare made of materials which may be disposed of in an environmentallyfriendly manner after completed use of the filter. In this known filterelement, the filter element is stiffened so that at least one insert iscomposed of a base material to which a net is attached by means of oneor more hot-melt lines or points. The base material and the net are madeof combustible materials.

However, manufacture of a filter element according to this prior art iscumbersome and expensive.

THE OBJECT OF THE INVENTION

The invention provides a filter element where it is possible to apply aliquid mass to the surface of the filter element, said liquid masscreating a form of stiffening lattice for the filter element when itsolidifies.

The advantage of the manufacture of such a filter element, in additionto the fact that all the parts of which the filter element is made arecombustible, is that the filter element may be manufactured much morerapidly and inexpensively, as the manufacturing process itself issimplified considerably.

The selected materials thus result in a simplification of the structureof the filter element, as the moulded material constitutes a goodstiffening of the filter element.

Owing to the optimum stiffening of the filter elements, the requirementswith respect to an attachment system for such a filter element will beminimum, as further stiffening is not necessary. Thus, the filterelement per se constitutes a housing for the filter.

This is achieved according to the method in that the net is made byapplying a liquid mass to the outer and/or inner side of the filterelement by means of one or more nozzles, said nozzles being movablerelative to the filter element.

THE DRAWING

The invention will now be explained more fully with reference to thedrawing, in which

FIG. 1 shows a filter element with a moulded lattice according to theinvention,

FIG. 2 shows another embodiment of a moulded lattice according to theinvention,

FIG. 3 shows a further embodiment of a moulded lattice according to theinvention, and

FIG. 4 shows an attachment system for the filter element shown in FIGS.1-3.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Expedient embodiments of the invention will be described below withreference to the drawing. A filter element 1 manufactured according tothe method comprises a hollow outer insert 2 in which a hollow innerinsert is arranged. in this exemplary embodiment, both the outer insert2 and the inner insert are tubular with coinciding centre lines.

The outer insert 2 is composed of a base material comprising a filtermaterial 3 made of a resin/material, e.g. cellulose and polyester.

When the outer insert 2 is arranged concentrically relative to the innerinsert 3 and they are secured mutually by means of a bottom flange 10and a top flange 11, a liquid mass 5 is applied by means of a form ofnozzle 4 or the like which hardens by cooling or any other impact and isthus capable of providing the stiffening 6 necessary for the filterelement 1.

The top and bottom flanges 11, 10 may either be made of a relativelyresilient material, which per se may constitute a seal or top and bottomflanges 11, 10 and may be provided with independently interactingsealing means.

In an expedient embodiment, the liquid mass 5 is applied by means of oneor more sets of nozzles 4, 7, a set being composed such that one nozzle4 is moved in a fixed path, and another nozzle 7 is adapted to performan oscillating movement out of the fixed path (see FIG. 1).

In a particularly simple embodiment, the liquid mass 5 may be applied bymeans of one or more nozzles 4, which perform a repeated movementextending from the top of the filter element 1 to the bottom of thefilter element 1 and back, while the filter element 1 rotates about itsown longitudinal axis.

These application examples may be performed in that an applicator withthe nozzle 4 performs the mentioned movements, while the filter element1 is kept still. Another solution model is to allow the filter 1 torotate, preferably about a horizontal axis, which, however, is not anecessity, while the nozzles 4, 7 are kept still. Moreover, the filterelement 1 cannot rotate until liquid mass 5 is supplied from the nozzle4 or the nozzles 7, followed by supply from the nozzle 4 or the nozzles7, while the filter element 1 is moved in a combination of a rotatingand an oscillating movement.

In a further embodiment (see FIG. 2), a lattice may be moulded in that alarger number of nozzles 4, e.g. ten, are arranged preferably with thesame mutual spacing. The nozzles 4 are kept at rest above a filterelement 1, which is arranged such that it may rotate about itshorizontal axis (when the filter element lies down). When the filterelement 1 rotates, ten rings 8 of the liquid material 5 are producedhereby, which material hardens or solidifies subsequently. When the tenrings 8 have been formed, the nozzles 4 are moved in a reciprocalmovement extending in the axial direction of the filter element 1, whilethe filter element 1 rotates about its horizontal axis. This creates acurve 9 which may have the shape of a sine curve, where the upper apexis tangent to the closest ring 8 at one side, and the lower apex istangent to the closest ring 8 at the other side. The number of rings 8is here stated to be e.g. ten, but the number is not restricted to thisnumber. The number is adapted to the length of the filter element 1 andto the desired spacing between the individual rings 8.

To prevent waste of material, it may be an advantage that one or more ofthe outermost positioned nozzles 4 may be sealed off completely orpartly during the application of the liquid material 5.

The nozzles 4 may advantageously also be positioned alternately offsetrelative to the line on which it would be natural to position these, sothat every other nozzle 4 is arranged on a line of its own spaced fromthe intermediate nozzles 4. The effect of this is that when the filterelement 1 rotates to have the first lines of liquid material 5 applied,so that these lines essentially constitute rings 8 or circles whichextend around the filter element 1, the rings 8 or the circles will beclosed when the filter element 1 has performed one rotation. Then, thetwo rows of nozzles 4 begin to move in an oscillating movement. Thisoscillating movement may be in the same direction, in the oppositedirection or offset with a delay so that the apexes of the curves 9between the individual rings 8 or circles are offset along thecircumference of the filter element. The extent of the oscillatingmovement may be varied or adapted to the current dimension of the filterelement.

Liquid material 5 may be applied to the internal side of the filterelement 1 simultaneously with the application of liquid material 5 tothe outer side of the filter element 1. This may be done e.g. by movinga long arm inwards along the centre axis of the filter element 1, saidarm thus following the movement of the external nozzles 4.

The applied lattice 8, 9 may comprise rings 8 or circles and/or curves9. A lattice comprising rings 8 may also be applied to the internalsurface of the filter element 1 and curves 9 to the external surface ofthe filter element 1 or vice versa. A combination of these examples ofrings 8 and/or curves 9 may be used for achieving the best stiffeningfor a given dimension of a filter element.

It is also possible to have an embodiment in which the nozzles 4 arekept at rest and the filter element 1 rotates, at the same time as thefilter element 1 moves in an oscillating movement in the direction ofthe centre axis.

In a further embodiment (see FIG. 3), a suitable number of rings 8 orcircles are applied, as mentioned in the above embodiment, followingwhich liquid material 5 is applied in a coherent curve 9 extending fromone end of the filter element 1 towards the other end of the filterelement 1 and back. This course is repeated until the curve 9 meets“itself” or intersects itself again.

In connection with the mounting of the filter element 1, where it isimportant that the admitted air does not leak past the filter element 1,a gasket/seal (not shown in the drawing) is used, likewise comprising aresin/material, e.g. foaming PU.

The outer insert 2 as well as the inner insert may basically have anyconfiguration, e.g. conical. The conical configuration will mean thatone flange, the bottom flange 10, may be omitted, whereby a filter maybe manufactured at lower cost. With the greatest cross-section orientedtoward the suction side, the conical configuration will thus cause thecross-section to increase through the filter, whereby the air speeddiminishes.

FIG. 4 shows an attachment system 12 to which the filter element 1 isattached. The attachment system 12 is made of a metallic or other hardmaterial and comprises an upper attachment part 13 as well as a lowerattachment part 14 relative to the upper attachment part 13, theconnection between the two attachment parts 13, 14 being provided by asuspension means 17.

In this exemplary embodiment, the upper attachment part 13 comprises aflange comprising defined edges 19 on the side oriented toward the lowerattachment part 14, said edges 19 having a mutual distance whichcorresponds to the external width of the top flange 9 of the filterelement, so that the edges 19 engage and support the sides of the topflange 9. A V-shaped suspension part 18 forming part of the suspensionmeans 17 is arranged between the defined edges 19 and oriented in thesame direction. The suspension part 18 is attached to the flange 13 byspot welding, and a handle 22 for attachment of the attachment system 12is mounted opposite the suspension part 18.

The lower attachment part 14 comprises a plate with an opening 20, andtwo defined edges 19 with the same mutual spacing as the defined edges19 on the upper attachment part 13 are provided on the side of the plate14 which is oriented toward the upper attachment part 14. Thus, theedges 19 correspondingly engage and support the sides of the bottomflange 10. A hooked rod 15 is inserted via the opening 20, with the hookpart 21 arranged in the suspension part 18. The hooked rod 15 thusconstitutes a second part of the suspension means 17.

As indicated by the name, the hooked rod 15 comprises a hook and a rod,said rod comprising threads 16 at its free end, i.e. opposite the hookpart 21, and when the hook part is thus placed in the suspension part 18(indicated by dashed line), the lower attachment part 14 is attached tothe upper attachment part 13 by screwing of a wing or fly nut 23.

The configuration of the upper attachment part 13 and the lowerattachment part 14, respectively, should be regarded more as beingillustrative than being an exact embodiment of the invention, as theseattachment parts may very well be configured differently.

Correspondingly, the suspension means 17 may be provided by othersolution models, e.g. by screw devices or by a wall which adjoins theinner insert, and which thus constitutes an additional reinforcement.

1. A method of manufacturing a filter element for use in connection withe.g. gas turbines and comprising a hollow outer insert in which a hollowinner insert is arranged centrally relative to the outer insert, saidinserts comprising end edges to which a top flange is secured at oneend, said inserts being stiffened by a net, characterized in that thenet (6) is made by applying a liquid mass (5) to the outer and/or innerside of the filter element by means of one or more nozzles (4, 7), saidnozzles (4, 7) being movable relative to the filter element (1).
 2. Amethod of manufacturing a filter element according to claim 1,characterized in that, during the application of moulding mass (5) inone or more rings (8), one or more nozzles (4, 7) are stationary in thelongitudinal direction of the filter element (1), while the filterelement (1) rotates a number of rotations about its longitudinal axis,on which one or more nozzles (4, 7) oscillate with an oscillationgreater than or equal to the distance between two rings (8) and smallerthan or equal to the length of the filter element (1) for theapplication of connecting lines (9) between the rings (8).
 3. A methodof manufacturing a filter element according to claim 1 or 2,characterized in that the rings (8) of moulding mass (5) are appliedsuch that they extend helically with one or more rings (8) along theouter and/or inner surface of the filter element (1).
 4. A method ofmanufacturing a filter element according to claim 1 or 2, characterizedin that one or more nozzles (4, 7) apply moulding mass (5) in rings (8)along the outer and/or inner surface of the filter element (1), saidrings being arranged in planes essentially parallel with the end faces(10, 11) of the filter element.
 5. A method of manufacturing a filterelement according to claims 1-4, characterized in that one or morenozzles (4) first apply moulding mass (5) in rings (8), following whichthe filter element (1), during rotation about its longitudinal axis, ismoved to and fro in its longitudinal direction with an oscillationgreater than or equal to the distance between two rings (8) and smallerthan or equal to the length of the filter element (1) for theapplication of connecting lines (9) between the rings (8).
 6. A filterelement manufactured by the method according to claims 1-5,characterized in that the stiffening (6) of the filter element (1) isformed by a solidified moulding mass (5).
 7. A filter element accordingto claim 6, characterized in that the filter element (1) is made ofcombustible materials.